1. Field of the Invention
This invention relates to an improved housing construction for a gas generator or inflator that utilizes the combustion of a solid gas generant composition for the rapid generation of a clean gas that is particularly useful for rapidly filling vehicle inflatable cushion restraint systems for the protection of the occupants from severe impact and possible injury during a collision.
2. Description of the Prior Art
Gas generators that utilize combustible solid gas generant compositions are known in the prior art. Common features of such generators that are used for the inflation of cushion restraint systems are the inclusion in a housing of a gas generant composition containing a pelletized alkali metal azide and means to filter and to cool the gas positioned between the gas generant composition and gas discharge orifices, as defined by the housing. Such compositions are considered advantageous for use in vehicle inflatable cushion restraint systems because the product of combustion is mainly nitrogen, an inert gas, and the speed of reaction or burning thereof, upon ignition, may be selected to be such as to effect the generation of gas at a very rapid rate but without detonation. Such constituents that burn rapidly, however, usually burn with a temperature of about 1000.degree. C., and develop a pressure in the housing in excess of 2000 psia.
Accordingly, among the problems associated with such prior art gas generators has been the containment of the high pressure gas producing reaction within a housing of acceptable weight and bulk. For example, U.S. Pat. No. 3,984,126 for an INFLATOR FOR VEHICLE OCCUPANT RESTRAINT SYSTEM, U.S. Pat. No. 4,116,466 for a FLUID SUPPLY FOR OCCUPANT RESTRAINT SYSTEM, and U.S. Pat. No. 4,296,084 for METHOD OF AND APPARATUS FOR GAS GENERATION all disclose the use of steel for the primary pressure chamber components of a gas generator in order to contain the pressure generated by the gas generant as it burns at near explosive rates. Current production gas generators for inflating automobile safety air bags also utilize steel structural components. Such gas generators may weigh between 900 to 1200 grams. When installed in a steering wheel hub in an automobile they add significant weight to the steering column. Steering column weight and generator vibration impact would both be reduced with a lighter weight gas generator. A large weight savings may be accomplished if the steel structural components of the prior art gas generators or inflators were converted or replaced by aluminum components. Forms of inflators that utilize aluminum for the housing structure are disclosed and claimed in copending application bearing Ser. No. 595,774, filed on April 2, 1984, by Wilbur J. Ahlf et al for INERTIA WELDED INFLATOR and in copending application bearing Ser. No. 595,803, filed on April 2, 1984 by Gary V. Adams et al for AUTO IGNITION DEVICE, both of which applications are assigned to the assignee of the present invention. However, the use of aluminum components in a gas generator presents a major problem. This is for the reason that at elevated temperatures in the 650.degree. F. (343.degree. C.) range, aluminum degrades. As a result, a gas generator comprised of aluminum components loses so much strength at such elevated temperatures that it probably would not pass the "bonfire" tests that such pyrotechnic devices must undergo without fragmentation in order to qualify for a low hazard shipping classification.